Drop-on-demand ink jet printing systems eject ink drops from printhead nozzles in response to pressure pulses generated within the printhead by either piezoelectric devices or thermal transducers, such as resistors. The printheads typically include a manifold that receives ink from an external ink supply and supplies ink to a plurality of pressure chambers. Each pressure chamber is fluidly coupled to the manifold by an inlet and to a nozzle, which is an opening in an external surface of the printing system, by an outlet. On a side of the pressure chamber opposite the fluid path to the nozzle, a flexible diaphragm layer overlies the pressure chamber and a piezoelectric or thermal transducer is positioned over the diaphragm layer.
To eject an ink drop from a nozzle, an electric pulse activates the piezoelectric device or thermal transducer, which causes the device or transducer to bend the diaphragm layer into the pressure chamber. This movement urges ink out of the pressure chamber through the outlet to the nozzle where an ink drop is ejected. Each piezoelectric device or thermal transducer is individually addressable to enable the device or transducer to receive an electrical firing signal. Each structure comprised of a piezoelectric or thermal transducer, a diaphragm, a pressure chamber, and nozzle is commonly called an inkjet or jet. When the diaphragm rebounds to its original position, the ink volume in the pressure chamber is refilled by capillary action of the inlet from the manifold.
Many ink jet printing systems eject drops of various colored inks. The inkjets in the system are configured to enable the differently colored drops to form color images on an image receiving member that is positioned opposite the printing system. In a common embodiment, an inkjet printer is configured to emit drops of a predetermined number of different ink colors onto the image receiving member. Combinations of the various ink colors on the image receiving member generate images with a wide range of colors. Common examples of such systems include cyan, magenta, yellow, black (CMYK) printing systems, as well as systems that use different numbers and colors of inks to generate color images. In some multicolor printing systems, separate printheads exclusively eject ink having only one of the predetermined colors. Other printing systems include a multicolor printhead with separate groups of inkjet ejectors. Each group of inkjet ejectors in the multicolor printhead is fluidly coupled to a manifold that supplies only one of the predetermined colors to the pressure chambers in the group of inkjet ejectors. The added complexity of supplying multiple ink colors to the inkjet ejectors and ensuring that ink of one color does not contaminate ink of another color presents a challenge to the design of multicolor printheads. Consequently, improvements to inkjet ejector isolation in multicolor printheads are desirable.